Tensioning system for an endless track system

ABSTRACT

Endless track system tensioning system comprising: Tensioner having a cylinder and a piston within the cylinder forming a variable volume chamber containing liquid. Reservoir containing liquid and gas fluidly connected to the cylinder chamber. Conduit fluidly connected between the chamber and the reservoir allowing liquid to flow therebetween to move a position of the piston. The gas applying hydrostatic pressure to liquid biasing the piston toward an extended position, biasing an idler wheel assembly against an endless track. Valve disposed along the conduit for controlling liquid flow through the conduit, movable between: Open position in which liquid is allowed to flow, rendering piston movable, allowing for relative movement between a frame and an idler wheel assembly. Closed position in which liquid is prevented from flowing rendering piston effectively immovable within the chamber, effectively preventing relative movement between frame and idler wheel assembly.

CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 15/565,450, filed Oct. 10, 2017, entitled “Dynamic TensionerLocking Device for a Track System and Method”. The '450 Application isthe United States National Stage of International Application No.PCT/CA2016/050419, filed Apr. 11, 2016, entitled “Dynamic TensionerLocking Device for a Track System and Method”. Via the '419 Application,the present application claims priority to U.S. Provisional PatentApplication No. 62/146,113, filed Apr. 10, 2015, entitled “DynamicTensioner Locking Device for a Track System”. The '450 Application isalso a continuation-in-part of U.S. patent application Ser. No.15/515,197, filed Mar. 29, 2017, entitled “Track System Having LowVibrations”. The '197 Application is the United States National Stage ofInternational Application No. PCT/2015/050978, filed Sep. 29, 2015,entitled “Track System Having Low Vibrations”. Via the '197 Application,the present application claims priority to U.S. Provisional PatentApplication No. 62/057,110, filed Sep. 29, 2014, entitled “Track SystemHaving Reduced Vibrations”; and to U.S. Provisional Patent ApplicationNo. 62/146,140, filed Apr. 10, 2015, entitled “Progressive DampingSystem for a Track System”. The entirety of each the foregoingapplications is incorporated herein by reference.

FIELD

The present technology relates to tensioning systems for endless tracksystems.

BACKGROUND

The present technology generally relates to track systems and tractionassemblies with tensioning devices that are used as wheel replacementfor typically wheeled vehicles such as, but not limited to, farming andagricultural vehicles (e.g., tractors, harvesters, etc.) andconstruction and industrial vehicles (e.g., excavators, combines,forestry equipment, etc.) and power sports vehicles (e.g., ATV's, UTV's,etc.).

Several normally wheeled vehicles and particularly heavy wheeledvehicles (e.g., farming tractors, front loaders, harvesters, etc.) oftenhave their wheels replaced by track systems that use an endless tractionband (also called endless tracks) instead of a tire for propulsion orfor steering. Vehicles equipped with track systems typically haveimproved floatation and traction, particularly when operated over softterrains.

Endless tracks have been used on such vehicles to increase surface areain contact with the ground. This increased footprint results in a lowerforce per unit area on the ground being traversed than that of the samevehicle having conventional wheels (and being of the same weight).

In a typical conventional an endless track system, an endless track isdriven by a sprocket in which teeth of the sprocket engage links of thetrack to drive the track, and thus the vehicle, forward. Support wheelsare typically conventionally attached to the vehicle through independentsuspensions and roll over the track, which is in contact with theground. In such cases, the support wheels typically do not drive thevehicle forward, as only the sprocket is used for providing movement.The direct engagement of the sprocket does not allow for track slippagerelative to the sprocket and/or due to friction between track andsprocket.

During operation, some components of such conventional track systems,particularly the idler wheels and support wheels, can experience unevenload distributions, especially upon braking. Braking events generallyprompt an upward movement of the idler wheel which affect the tension ofthe endless track. This is particularly true for the idler wheelslocated towards the front of the track system. As upward movement of theidler wheels is generally desired when encountering varying obstacle,terrain variation and/or debris ingestion, conventional tracked vehiclesare typically equipped with one or more tensioner systems adapted tosubstantially maintain the track at a predetermined tension in operationover various terrain profiles. Such tensioner systems aim at avoidinghaving the track slide off (disengage) the sprocket and/or the idlerwheels during a sudden maneuver or a turn. Typically, such tensionersystems may also prevent excessive loads from being applied to theendless track, to the vehicle drive wheel, and to the vehiclesuspension.

Additionally, track tension may impact power efficiency. In somesituations, an over-tensioned or under-tensioned track may lead to powerloss from excess friction and may accelerate wearing of the tracksystem. However, radially upward movement of the idler wheels uponbraking must be restrained as tension of the track is decreased(loosening the endless track leading to ratcheting of the track). Assuch, decreased tension in the endless track upon braking hinders theproper functioning of the track system and decreases the brakingefficiency of the track system. Furthermore, upward movement of theidler wheels upon braking increases wearing of the track system, in partdue to ratcheting but also due to the overall deformation of the tracksystem. As such, the tensioner system in the track system aims atmaintaining the perimeter defined by the wheels generally equal orsuperior to the nominal perimeter of the track.

Track tension is typically controlled by moving a sprocket or idlerwheel that engages the track. A conventional passive mechanism formoving the sprocket or idler wheel is a track tensioner employing agrease-filled cylinder or an oil filled cylinder using an accumulatoracting as a spring, which is referred to as a dynamic tensioner. Apiston in the cylinder moves as grease is added or removed through afitting. By its motion, the piston moves the sprocket or idler wheelrelative to the track thereby causing the sprocket or idler wheel toeither extend into the track path and increase the tension of the trackor to withdraw from the path of the track and decrease the tension ofthe track.

Indeed, in track systems, the resultant force from track tension andtrack friction can induce a torque around the idler frame pivot,resulting in the rotation of the idler frame thereabout. This rotationthen generally causes the idler wheel located at one end of the idlerframe to move circularly about the radius of the idler frame pivotpoint, while causing the road wheels located at the other end of thetandem frame to move in the opposite direction circularly about theradius of the idler frame pivot point. This results in an increased loadon the wheels, which are urged against the ground. The rotation of theidler frame can also cause the trailing portion of the track system torise. This uneven load distribution can reduce the efficiency of thetrack system and even lead to premature failure thereof.

Moreover, some safety regulations in countries require that agriculturaltracked vehicles be able to immobilize themselves from a given speedwithin a certain distance and/or meet a deceleration value. Thoserequirements are such that current mechanisms are inefficient if notdeficient at avoiding the ratcheting phenomenon as described above.

Hence, there is a need for an improved track system having a dynamic oractive track tensioning system that may mitigate at least someshortcomings of prior art track systems.

The required tensioning system should be able to allow rotationalmovement of the front wheel when the vehicle is in normal operation modeand be able to block, or limit, such movement in a braking event toavoid or at least limit the ratcheting of the sprocket wheel or drivewheel.

Rear suspensions for mountain bikes face similar issues as theirsuspension tends to compress when the user pedals, and such compressionreduces the efficiency of the biker's pedaling. Solutions have beendeveloped to adjust the damping of the suspension in relation with tothe shock force applied on the suspension. An example of such a solutionmay be found in U.S. Pat. No. 8,770,360 in which an inertial valve isused to modulate the damping of the suspension element. However, suchsolution provides a means for maintaining the suspension blocked duringoperation and for unlocking the suspension element when an obstacle ishit. Furthermore, such solutions are configured to absorb a limitedshock or force.

SUMMARY

A track system in accordance with the principles of the presenttechnology may mitigate at least some of the shortcomings of prior tracksystems by having a dynamic tensioning system adapted to selectivelyhamper tensioner compression upon occurrence of selective directionalforce.

Hence, a track system in accordance with the principles of the presenttechnology generally comprises a drive wheel configured to be mounted toan axle of a vehicle, a support frame (or support frame assembly)configured to be mounted to the vehicle, front and rear idler wheels,typically respectively mounted at the front and at the rear of the tracksystem, support (road) wheels, typically mounted longitudinally betweenthe idler wheels, and an endless traction band disposed about the drivewheel, the idler wheels and the support wheels.

The traction assembly comprises a traction band dynamic tensioningsystem mounted to the support frame and configured to controllablytension the traction band around the wheels of the traction assembly.

In accordance with an aspect of the present technology, a dynamicblocking tensioning device is attached to the support frame and bias anidler wheel so as to impart a force on the endless track to maintain anoptimal track tension, decreasing endless track slippage relative to thedrive wheel, idler wheels and road wheels, allowing for optimal trackmovement along all types of terrain and in combination with a preferredincreased vehicle footprint, increasing the overall vehicle traction andmobility of the vehicle.

The dynamic blocking tensioning device is typically mounted at the frontor at the rear of the support frame such as to operatively bias thefront idler wheels or the rear idler wheels against the track. As such,the tensioner applies the required tension to the track while allowingfor some flexibility upon encountering obstacles or terrain variationswhile having the ability to block or lock tensioning upon the occurrenceof target directional forces.

In accordance with an aspect of the present technology, a tensioningdevice comprises an actuator, a fluid tank in fluid communication withthe actuator through a tank return flow path, an accumulator in fluidcommunication with the actuator through an accumulator flow path,whereby an inertia valve is operatively connected to the fluid flow pathas to impede or block the flow upon the occurrence of a directional orinertial force applied to the track system or tracked vehicle.

In accordance with the principles of the present technology, thetensioning device exerts a variable force on the endless track in orderto increase, decrease, or maintain endless track tension as needed in adynamic manner. When the variable force is increased, the endless trackwill achieve a greater tension around the wheels and decrease trackslippage relative to the drive wheel. When the variable force isdecreased, the endless track will achieve a lower tension around thewheels. Decreasing track tension, especially when increased tracktension is not needed, may also reduce wear of the mating components.

In accordance with the principles of the present technology, the dynamictensioner locking device for a track system is preferably locatedbetween an idler wheel and the support frame. Alternatively the dynamictensioner locking device for a track system may be situated between thesupport frame and a support member operatively connected to the idlerwheel so long as the resulting tensioner effect is to bias the idlerwheel as to apply a desired tension to the endless track of the tracksystem.

In accordance with the principles of the present technology, the dynamictensioner locking device for a track system comprises an inertial valveconfigured to obstruct or at least impede the fluid, preferablyhydraulic fluid, from flowing between an actuator/cylinder chamber and afluid tank/reservoir or accumulator, thus preventing the application ofa variable tension to the track system upon occurrence of targetdirectional force. An exemplary directional force may be the inertialforce resulting from braking of the tracked vehicle. In such example,upon braking of the tracked vehicle, the inertial force will direct anobstructing member, such as a ball, or cylinder, preferably made frommetallic material through the fluid flow path, thus impeding or blockingthe fluid flow and preventing the variation of the tensioner. For somevehicle, the force applied on the blocking apparatus may be significant.Accordingly, the system may be adapted to reduce the flow of fluidinstead of totally blocking the flow to avoid failure. The blockingdevice, such as the ball, or valve, may thus be positioned in two ormore positions as to offer better granularity in the flow control.

As the flow of fluid will be blocked or reduced between the cylinder andthe inertial valve, the length of the tensioner shall remain locked orconstant as to allow the idler wheel to apply tension on the track byavoiding an inward displacement of the idling wheel within the tractionassembly.

Alternatively, according to another aspect of the present technology,the vehicle brake could be connected to a solenoid and trigger blockingof the tensioner as to electronically result in the blocking of thevariable tension application.

In accordance with another aspect of the present technology, dynamictensioner locking device for a track system comprises a piston rodcarrying a piston and a tube defining a piston chamber. The piston isconfigured for reciprocal movement within the piston chamber. Areservoir chamber is defined by the tensioner and includes a dividerconfigured to move to vary a volume of the reservoir chamber toaccommodate fluid displaced from the piston chamber by the piston rod.The dynamic tensioner locking device for a track system also includes afluid passage connecting the piston chamber and the reservoir chamberand a valve having a first position and a second position. The valvepreferably permits a first rate of fluid flow through the flow passagein the first position and the valve permits a second rate of fluid flowthrough the flow passage in the second position. Movement of the dividermoves the valve between the first and second position. The valve mayalso offer more than two positions to offer better granularity.

In accordance with another aspect of the present technology, the dynamictensioner locking device for a track system comprises a tube and apiston rod carrying a piston for reciprocal movement within the tube.The piston and the tube define a first fluid chamber. A second fluidchamber is defined by the damper. The dynamic tensioner locking devicefor a track system also comprises a first valve configured to movebetween a first position and a second position in response to anincrease in the volume of fluid within the second chamber and a secondvalve configured to move between a first position and a second positionin response to a deceleration force applied to the tensioner.

In accordance with another aspect of the present technology, atensioning device comprises an actuator or cylinder and piston, a fluidtank also referred to as an accumulator in fluid communication with theactuator through a tank return flow path, whereby an inertia valve isoperatively connected to the fluid flow as to impede the flow upon theoccurrence of a directional or inertial force applied to the tracksystem.

In accordance with another aspect of the present technology, a methodincluding the steps of determining a desired tension of the track on thetrack vehicle, generating a fluid pressure through the rotation of anidler wheel on said tracked vehicle, increasing the tension of the trackof the tracked vehicle by extension of the idler wheel with said fluidpressure, decreasing a tension of the track of the tracked vehicle byretraction of the idler wheel through a relieve of said fluid pressure,reversibly hampering or reversibly obstructing the dynamic tensionadjustment using an inertial valve interrupting fluid flow between theaccumulator and fluid tank.

In accordance with the principles of the present technology, a methodincluding the steps of determining a desired tension of the track on thetrack vehicle, generating a fluid pressure through the rotation of anidler wheel on said tracked vehicle, increasing the tension of the trackof the tracked vehicle by extension of the idler wheel with said fluidpressure, and decreasing a tension of the track of the tracked vehicleby retraction of the idler wheel through a relieve of said fluidpressure, dynamically blocking the tensioner upon the occurrence of aselected directional force.

The technology is directed to a track system for a vehicle, the tracksystem comprising a drive wheel operatively mounted to the vehicle, asupport frame, an idler wheel pivotally mounted on the support frame; anendless track disposed around the drive wheel, and the idler wheel, theendless track defining an overall perimeter of the track system and adynamic tensioner attached between the idler wheel and the supportframe, the dynamic tensioner being adapted to substantially maintain thelength of the dynamic tensioner when an acceleration of the track systemreaches a predetermined value.

In accordance with the principles of the present technology, the dynamictensioner may be a fluid-based suspension element fluidly connected to areservoir of fluid. The dynamic tensioner comprises a mean adapted tolimit a displacement of fluid between the fluid-based suspension elementand the reservoir when the acceleration of the track system reaches thepredetermined value. The fluid-based suspension element may comprise ahollow portion adapted to slidingly receive a piston, the hollow portiondefining a chamber between the piston and a closed end of the hollowportion.

Still in accordance with the principles of the present technology, themean adapted to limit a flow of fluid comprises a moving element adaptedto obstruct, or partially obstruct the fluid path between the chamberand the reservoir.

In accordance with the principles of the present technology, the meanadapted to limit a flow of fluid may be an inertial valve, or an activeflow control mean, such as but not limited to, a solenoid.

The active control mean is triggered by a signal. The signal may begenerated by a switch, or an accelerometer. Accordingly, a controllermay be required to translate the signal to be used by the solenoid.

In accordance with the principles of the present technology, the dynamictensioner may be fluidly connected to a fluid device adapted to change aquantity of fluid contained in the reservoir. This may help adjustingthe length of the tensioner. The fluid device, such as but not limitedto, a hydraulic pump, may be triggered by a sensor.

In accordance with the principles of the present technology, a securitysystem, such as a release valve, may be fluidly connected to the systemto relieve excess pressure.

The technology is further directed to a method for controlling a tensionin an endless track disposed around a plurality of wheels pivotallymounted on a support frame of a track system, the track system beingoperatively mounted to a vehicle, at least one of the plurality ofwheels being operatively mounted to a dynamic tensioner, the dynamictensioner being operatively mounted on the support frame, the methodcomprising the step of substantially maintaining the length of thedynamic tensioner when an acceleration of the track system reaches apredetermined value.

In accordance with the principles of the present technology, the methodmay comprise the step of determining the acceleration of the tracksystem. The method may also comprise the steps of limiting a flowbetween a fluid-based suspension element and a reservoir forsubstantially maintaining the length of the dynamic tensioner if theacceleration reaches the predetermined value; and allowing a flowbetween the fluid-based suspension element and the reservoir forallowing variation of the length of the dynamic tensioner if theacceleration is below the predetermined value.

Still in accordance with the principles of the present technology, themethod may further comprise the steps of adding fluid in the reservoirfor increasing track tension if the acceleration reaches a predeterminedvalue; and removing fluid in the reservoir for allowing variation of thelength of the dynamic tensioner if the acceleration is below thepredetermined value.

The method may further comprise the step of obtaining the signal from anaccelerometer or a general switch.

Embodiments of the present technology each have at least one of theabove-mentioned object and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presenttechnology that have resulted from attempting to attain theabove-mentioned object may not satisfy this object and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects and advantages ofembodiments of the present technology will become apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present technology, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1 is a perspective view of a vehicle having mounted thereto fourtrack systems in accordance with the principles to the presenttechnology.

FIG. 2 is a perspective view of one of the track system of FIG. 1.

FIG. 3 is a side view of the track system of FIG. 2.

FIG. 4 is a side view of the track system of FIG. 2.

FIG. 5 is a side view of another embodiment of a track system inaccordance with the principles to the present technology, without theendless traction band having the dynamic tensioner locking deviceinstalled thereto.

FIG. 6A-F are schematic views of an exemplary dynamic tensioner lockingdevice for a track system in accordance with the principles to thepresent technology.

FIG. 7 is a schematic view of an exemplary functioning of the dynamictensioner locking device.

FIG. 8 is a close up view of another embodiment of a track system inaccordance with the principles to the present technology, having thedynamic tensioner locking device installed thereto.

FIG. 9 is a side view of another embodiment of a track system inaccordance with the principles to the present technology, having thedynamic tensioner locking device installed thereto.

FIG. 10 is a schematic view of another embodiment of the dynamictensioner device in accordance with the principle of the presenttechnology.

FIG. 11 is a schematic view of another embodiment of the dynamictensioner device in accordance with the principle of the presenttechnology.

FIG. 12 is a schematic view of another embodiment of the dynamictensioner device in accordance with the principle of the presenttechnology.

FIG. 13 is a schematic view of another embodiment of the dynamictensioner device in accordance with the principle of the presenttechnology.

FIG. 14 is a schematic view of another embodiment of the dynamictensioner device in accordance with the principle of the presenttechnology.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

A novel dynamic tensioner locking device for a track system will bedescribed hereinafter. Although the technology is described in terms ofspecific illustrative embodiments, it is to be understood that theembodiments described herein are by way of example only and that thescope of the technology is not intended to be limited thereby.

Referring first to FIG. 1, a typical embodiment of an endless tracksystem 20 is shown.

FIG. 1 shows four (4) endless track systems each mounted to a vehicle10. The vehicle 10 is a front-loader typically used in the area ofconstruction. The track systems 20 are used to replace the wheels whichare typically used on such vehicle 10.

Referring now to FIGS. 2 and 3, a typical embodiment of an endless tracksystem 20 is shown. In such a typical endless track system, the tracksystem 20 comprises a drive wheel 22 configured to be mounted to theaxle (not shown) of the vehicle 10. The drive wheel 22 defines arotation axis 23 about which it rotates. The drive wheel 22 comprises,along its periphery 24, a plurality of evenly disposed sprocket teeth 26configured to engage drive lugs (not shown) located on the inner surface30 of the traction band 28. In the present embodiment, the drive wheel22 is a sprocket wheel.

The track system 20 typically comprises a frame assembly 34 pivotallymounted to the drive wheel 22. In the present example of endless tracksystem, the frame assembly 34 is pivotally mounted to the drive wheel22. Understandably, in other embodiments, the frame assembly 34 could beconfigured to be mounted to the vehicle 10 using other mounting method,such as replacing the final drive or mounting the track system on a freerotating shaft of the vehicle. In yet other embodiments, the frameassembly 34 may comprise an attachment frame or assembly configured tosecure the frame assembly 34 to the vehicle 10.

Typically, the endless track system 20 comprises at least one idlerwheel which is pivotally mounted with regard to the frame assembly 34.In the present example, a front pivoting point 40 defines a rotationaxis 41 while a rear pivoting point 42 defines a rotation axis 43. Asbest shown in FIG. 3, the rotation axis 41 is longitudinally located infront of the drive wheel rotation axis 23 while the rotation axis 43 islocated longitudinally behind the drive wheel rotation axis 23.

In other embodiments, the idler wheel 44 may be pivotally mounted on atandem structure with one or more road wheels 46 or 50, which tandemstructure is pivots with regard to the frame assembly 34.

The track system 20 also comprises a traction band or endless belt 28disposed about the drive wheel 22, the idler wheels 44 and 48 and theroad wheels 46 and 50. The traction band 28 is typically made fromreinforced elastomeric material and comprises an inner wheel engagingsurface 30 and an outer ground-engaging surface 32.

Though not shown in the figures, the outer surface 32 of the tractionband 28 typically comprises traction lugs configured to engage theterrain over which the track system 20 is operated.

Now referring to FIG. 5, an example of a tracked vehicle having adynamic tensioner locking device 200 operatively connected to an idlerwheel 48 and to the frame assembly 134 is shown. A typical tensionerdevice is generally embodied as a damper or cylinder which ensures thatthe displacement of the idler wheel with regard to the frame assembly islimited or allows re-positioning of the idler wheel in a position toprovide tension in the endless track within a range of predeterminedvalues. Another embodiment of a track system having a dynamic tensionerlocking device 200 is shown in FIG. 9.

Now referring to FIGS. 6A-F and 7, an embodiment of a dynamic tensionerlocking device 200 for a track system is shown at various time of anevent of inertial force, such as a hard braking event. It shall beunderstood that the FIGS. 6 and 7 are schematic diagram and that certaincomponents were removed for the sake of clarity. The dynamic tensionerlocking device 200 of this embodiment preferably comprises a fluid-basedsuspension element 200 a including a cylinder 206. The cylinder 206typically comprises a plunger or piston 208 hermetically or sealinglyinserted in a chamber 210. The cylinder 206 is in fluid communicationwith a fluid reservoir or accumulator 204 using any connecting membersuch as a conduit 224. The connecting member 224, the interior chamber,or compression chamber 210 and the reservoir 204 comprise a liquidfluid, such as oil, and a compressible gas fluid, such as nitrogen (N2).The piston 208 is slidingly engaged with an interior surface of thechamber 210. Understandably, any other type of fluid-based suspensionelement may be used without departing from the principles of the presentinvention.

As the force on the tensioning device 200 is increased, the piston 208moves toward a closed opening of the cylinder, the liquid fluid ispushed in the connecting member 224 and the reservoir 204. The portionbetween the piston 208 and the closed end of the cylinder is known asthe compression chamber 210. As the piston 208 is pushed in the cylinder206, the taken volume of the piston is pushed in the reservoir. As aresult, the fluid reservoir 204 is typically provided to act as a springby receiving the fluid in excess.

Thus, the reservoir chamber 204 acts as an accumulator that acceptsexcess tensioning fluid upon compression of the tensioner 212. The fluidis then returned to the compression chamber 210 upon expansion of thetensioner piston 208. Although the illustrated reservoir chamber 204 isdefined by a separate structure from the main tensioner body 206 (around reservoir, in this instance), in other arrangements the reservoir204 and tensioner body 206 may share common structural components.Furthermore, other suitable compensation mechanisms may also be used.

In the illustrated arrangement, the reservoir chamber 204 comprises twotypes of fluid, such as, but not limited to, hydraulic oil and nitrogen.The connecting member conduit 224 comprises an inertial blockingmechanism 228, such as an inertial valve 228. The inertial blockingmechanism blocks or at least limits the flow of the fluid upon aninertial event, such as hard braking. Understandably, any inertialblocking mechanism allowing the tension to be maintained may be used.Typically, an inertial valve 228 comprising a valve body 214, an inertiaactuator 216, and a biasing member 218 operatively biasing the inertiaactuator 216 in an initial and inoperative position.

The inertia actuator may be embodied as a ball or elongated member 216,preferably made from metallic material to impart a significant mass tothe inertia actuator.

Understandably any type of suitable inertial valve configured to blockor limit the flow of a fluid upon occurrence of a selected force couldbe used without departing from the principle of the present technology.

Also, the dynamic tensioner 200 is typically configured to block orsubstantially reduce the flow at a predetermined offload or force. Inoperation, when an inertial force is applied, the inertial actuator 216completely or partially moves across the connecting member, thusblocking or limiting the flow between the reservoir and the chamber. Asa result of the flow of the liquid fluid being blocked, the piston 208may not further move within the chamber as the compressibility of thefluid liquid is very low or null. As a result of the flow of the liquidfluid being limited, the movement of the piston 208 within the chamberis slowed or stopped. On the other end, the piston 208 is pushed andmoves the fluid by the force applied on the idler wheel as a result of abraking event. At this point, the length of the tensioner remainsgenerally locked or constant as to prevent the idler wheel to moveinwardly within the track system or slow down the inward movement of theidler wheel.

Broadly, the tensioner 212 provides movement between the idler wheel andthe frame of the track system. Such movement is useful to maintain thetension of the track upon crossing obstacle and uneven terrain and/oringesting debris. In some embodiments having suspension elements, themovement between the idler wheel and the frame limits tension variationwhen components are moving. The locking of the tensioner occurs onlyupon triggering of the inertial valve. Typically, the tensioner shall beblocked when a hard braking event occurs. It should be noted that thefloating piston may be replaced by other suitable separating structures(such as a flexible diaphragm, for example). Furthermore, a reservoirsealing cap desirably includes a valve (not shown) which allows thepressure within the reservoir chamber 204 to be adjusted. In somearrangements, the gaseous fluid component, i.e. the nitrogen 230, may bereplaced by an alternative compressible material, such as a memberformed of compressible closed-cell foam, for example.

Now referring to FIG. 6A, a schematic representation of the dynamictensioner locking device 200 for a track system is shown at an initialtension level. In operation, in response to terrain variations or thepresence of obstacles, the piston 208 is allowed to move within thecylinder 206 thus slightly decreasing the tension applied to the endlesstrack (FIGS. 6A-C). FIGS. 6B and 6C illustrate the event where thepiston is further moved within the cylinder. Likewise, when the terrainconditions are back to normal, the piston returns to its initialposition (FIG. 6D).

Upon occurrence of a triggered inertial event, such as the braking, ordeceleration of the vehicle, the actuator, such as the ball 216,laterally move in the conduit to interrupt the fluid flow path (FIGS.6E-F). Thus, as the liquid fluid is trapped between the cylinder and theactuator, any movement of the piston 208 in the cylinder 206 isimpossible or limited.

Now referring to FIG. 8, another embodiment of a dynamic tensionerlocking device for a track system using a solenoid valve 316 is shown.In such an embodiment, the dynamic tensioner locking device comprises anactuator 310 and a fluid tank also referred to as an accumulator 304operatively connected via a conduit or fluid flow path 312. A solenoidvalve 316 is configured to be closed upon activation from a signal fromthe inertial event. Typically, the solenoid valve shall be closed basedon the braking signals generated by a braking pedal or any other brakingmechanism. The closing of the solenoid valve interrupts or reduces thefluid connection between the accumulator and the chamber of thecylinder.

The dynamic tensioner locking device for a track system may furthercomprise one or more pressure sensors monitoring the fluid pressurewithin various portions of the fluid reservoir.

Now referring to FIG. 10, another embodiment of the dynamic tensionersystem is illustrated. The system 500 a comprises the accumulator, orreservoir 501 fluidly connected to the damping element or cylinder 502.An active fluid control mean 503, such as a solenoid valve, is adaptedto either allow or completely block the flow of fluid between thereservoir 501 and the cylinder 502 as to limit, preferably forbid,movement of the piston inside the cylinder. Optionally, a mean ormechanism adapted to allow flow of fluid at a predetermined pressure,such as relief valve 504, may be fluidly connected to the reservoir andto the piston. When the pressure in the system 500 a reaches a giventhreshold, the relief valve 504 is adapted to relieve pressure to avoidsystem failure or damaging the equipment. The active flow control mean,such as, but not limited to, a solenoid, may be controlled by acontroller 520 which receive a signal from any mechanism, such as, butnot limited to a brake pedal switch 522, an accelerometer 524, one ormore sensor 526 or any other switch 528.

Now referring to FIG. 11 representing a variation to the embodimentillustrated in FIG. 10. In system 500 b, the active fluid control mean505 is adapted to provide increased control or granularity of the flowof fluid. Further to totally blocking the flow, the valve 505 is able toallow a reduced flow rate by moving from a fully opened position to apartially opened or partially closed position. Understandably, the valve505 may be adapted to move in a plurality of positions to offer greatercontrol over the flow rate. This embodiment may further comprise apressure relief valve 504 in the case the pressure in the system is toohigh.

Referring now to FIG. 12 representing a similar system 500 c where thesolenoid valve is replaced by an inertial valve 506. Such valvecomprises a ball, or cylinder or the likes that is able to move in orderto block or limit the flow of fluid between the reservoir 501 and thecylinder 502. In a situation where the track system speed is changing,the ball tends to remain at its current speed. For instance, if thevehicle is braking, the speed of the whole system 500 c will diminish,but the ball, by its inertia, will temporarily remain at its originalspeed. The ball will thus move forward, pushed or moved by deceleratingforce 511, with regards to the track system as to intersect and blockthe fluid path and thus limit the piston's movement inside the cylinder502. It may also be necessary for such an embodiment to include apressure relief valve 504 to avoid excessive pressure that may damagethe system.

Now referring to FIG. 13 that represents a variation of the embodimentof FIG. 12. In system 500 d, the inertial valve 506′ is able to providetwo or more flow rate values. The ball or cylinder comprised in thevalve 506′ is able to move in one or more positions between the fullyopened position and the fully closed position when a force 511 isapplied on the inertial valve. As explained above, the force may comefrom deceleration or other event. It may be also necessary for thisembodiment to comprise a pressure relief valve 504 to avoid excessivepressure that may damage the system.

Another embodiment is schematically illustrated in FIG. 14. In thiscase, the system 500 e further comprises a relief valve 504′, a manifold509 and a hydraulic pump 510. The combination thereof is adapted to addor remove fluid from the system 500 e to either harden or soften thetensioner 502. An increased tension in the track system aims at furtherlimiting the ratcheting of the track while braking. The system may alsocomprise an analogical sensor 508 adapted to trigger the hydraulic pump510 when necessary. The system 500 e is provided with the solenoid valve503, but any other valve such as the inertial valve 506 may be used.

Now referring to all figures illustrating embodiments using a solenoidvalve. The solenoid valve may be triggered from a plurality ofmechanisms. For instance, a switch 522 may be operatively connected tothe brake pedal of the vehicle. In another embodiment, the switch 522may be installed inside the vehicle's cabin and within hand reach of theoperator so he can activate the valve in an emergency braking situation.Furthermore, an accelerometer 524 may be operatively connected to thesolenoid valve to trigger the latter when acceleration reaches a giventhreshold. An inertial system may also be used. Such system may comprisean element that is free to move with regards to the vehicle. Uponacceleration, said element will trigger the solenoid. Understandably,any other system adapted to detect a change of speed of a vehicle may beused to trigger the valve.

According to one embodiment, an external control system may actively orautomatically controls the position of the idler wheel 320 and thus atension of the track. Furthermore, the track tensioning system of thepresent technology may employ a manual controller that provides a drivecommand to the idler wheel for manually establishing, for example, ahigh and/or a low tension or the track. As such, in an active controlembodiment, an external control system would block or lock the variabletensioner to limit is variation in response to a selected event. Forinstance, the external system could be configured to actuate the dynamictensioning function upon braking of the vehicle.

Understandably, the dynamic tensioner locking device for a track systemmay function on a variety of different track system as long as thetension is controlled by the movement of a wheel. As such, the dynamictensioner locking device for a track system could be installed on asplit frame track system as shown in FIG. 9. Other embodiment could alsobe configured for various frame assembly without departing from theprinciples of the present technology.

Still referring to FIG. 8, in case of a braking event, the valve closes.In the closed condition, either the flow stops or barely circulates asto prevent, or limit, the track tensioner to compress. The objective isto prevent the endless track to ratchet by keeping the endless trackperimeter equal or shorter than the track system perimeter.

The valve may close either when an electric signal is sent by theoperator in a braking event or upon movement of an inertial device, suchas a ball. Also, the electric signal may also be triggered by aninertial device.

Modifications and improvements to the above-described implementations ofthe present technology may become apparent to those skilled in the art.The foregoing description is intended to be exemplary rather thanlimiting. The scope of the present technology is therefore intended tobe limited solely by the scope of the appended claims.

The invention claimed is:
 1. A tensioning system for an endless tracksystem, the endless track system having a frame, an idler wheel assemblyand an endless track extending around the frame and the idler wheelassembly, the idler wheel assembly being movable with respect to theframe for tensioning the endless track, the tensioning systemcomprising: a tensioner operatively connectable between the frame andthe idler wheel assembly of the endless track system for controllingrelative movement between the frame and the idler wheel assembly forapplying tension to the endless track, the tensioner including: acylinder; and a piston that is reciprocally movable within the cylinderbetween an extended position and a retracted position, the pistonsealingly engaging the cylinder for forming a variable volume chambercontaining a liquid, the piston being movable between the extendedposition and the retracted position in a plurality of intermediatepositions by changing a volume of the liquid contained within thechamber of the cylinder; a reservoir fluidly connected to the chamber ofthe cylinder, the reservoir simultaneously containing the liquid and agas, the gas in the reservoir being under pressure and applyinghydrostatic pressure to the liquid tending towards an increase in thevolume of liquid within the chamber of the cylinder, biasing the pistontowards the extended position, biasing the idler wheel assembly againstthe endless track; a conduit fluidly connected between the tensioner andthe reservoir allowing the liquid to flow between the chamber of thecylinder and the reservoir to change the volume of liquid within thechamber of the cylinder to move the piston within the chamber of thecylinder; and an inertial valve disposed along the conduit for allowingand preventing liquid flow through the conduit, the inertial valve beingmovable between: an open position in which the liquid is allowed to flowbetween the chamber of the cylinder and the reservoir, rendering thepiston movable within the chamber and allowing for relative movementbetween the frame and the idler wheel assembly; and a closed position inwhich the liquid is prevented from flowing between the chamber of thecylinder and the reservoir, rendering the piston effectively immovablewithin the chamber and effectively preventing relative movement betweenthe frame and the idler wheel assembly.
 2. The tensioning system ofclaim 1, wherein the inertial valve includes: a hollow body defining atleast part of the conduit; an inertia mass movable within the hollowbody from the open position to the closed position in response to anacceleration of the endless track system in a predetermined directionexceeding a predetermined acceleration threshold; and a spring connectedto the hollow body and to the inertia mass, the spring biasing theinertia mass toward the open position inside the hollow body.
 3. Thetensioning system of claim 2, wherein the inertial valve is movablebetween the open and closed positions in a plurality of intermediatepositions so as to provide a plurality of liquid flow rates within theconduit, rendering the piston movable within the chamber of the cylinderat a plurality of speeds.
 4. A tensioning system for an endless tracksystem, the endless track system having a frame, an idler wheel assemblyand an endless track extending around the frame and the idler wheelassembly, the idler wheel assembly being movable with respect to theframe for tensioning the endless track, the tensioning systemcomprising: a tensioner operatively connectable between the frame andthe idler wheel assembly of the endless track system for controllingrelative movement between the frame and the idler wheel assembly forapplying tension to the endless track, the tensioner including: acylinder; and a piston that is reciprocally movable within the cylinderbetween an extended position and a retracted position, the pistonsealingly engaging the cylinder for forming a variable volume chambercontaining a liquid, the piston being movable between the extendedposition and the retracted position in a plurality of intermediatepositions by changing a volume of the liquid contained within thechamber of the cylinder; a reservoir fluidly connected to the chamber ofthe cylinder, the reservoir simultaneously containing the liquid and agas, the gas in the reservoir being under pressure and applyinghydrostatic pressure to the liquid tending towards an increase in thevolume of liquid within the chamber of the cylinder, biasing the pistontowards the extended position, biasing the idler wheel assembly againstthe endless track; a conduit fluidly connected between the tensioner andthe reservoir allowing the liquid to flow between the chamber of thecylinder and the reservoir to change the volume of liquid within thechamber of the cylinder to move the piston within the chamber of thecylinder; a pump fluidly connected to a liquid source, and the pumpbeing fluidly connected to at least one of the reservoir, the chamber ofthe cylinder and the conduit for selectively changing an amount of theliquid contained inside the at least one of the reservoir, the chamberof the cylinder and the conduit; and a valve disposed along the conduitfor allowing and preventing liquid flow through the conduit, the valvebeing movable between: an open position in which the liquid is allowedto flow between the chamber of the cylinder and the reservoir, renderingthe piston movable within the chamber and allowing for relative movementbetween the frame and the idler wheel assembly; and a closed position inwhich the liquid is prevented from flowing between the chamber of thecylinder and the reservoir, rendering the piston effectively immovablewithin the chamber and effectively preventing relative movement betweenthe frame and the idler wheel assembly.
 5. The tensioning system ofclaim 4, wherein the pump is operable to pump liquid from the liquidsource to the at least one of the reservoir, the chamber of the cylinderand the conduit so as to bias the piston toward the extended positionfor increasing the tension applied by the tensioning system on theendless track.
 6. The tensioning system of claim 4, wherein the pump isoperable to pump liquid from the at least one of the reservoir, thechamber of the cylinder and the conduit to the liquid source so as tobias the piston toward the retracted position for decreasing the tensionapplied by the tensioning system on the endless track.